Cutting device for sewing machine



y 1959 c. J. M. BENINK ET AL 2,893,335

CUTTING DEVICE FOR SEWING MACHINE 3 Sheets-Sheet 1 Filed June 25, 1957 F'IG- 7 H 5 3 "Y m 5 u ik m hi 4/ v W ii ML July 7, 1959 c. J. M. BENlNK ETAL CUTTING DEVICE FOR SEWING MACHINE 3 Sheets-Sheet 2 Filed June 25, 1957 uly 1959 c. J. M. BENlNK ETAL 2,893,335

CUTTI NG DE\ IICE FOR SEWING MACHINE Filed June 25, 1957 3 Sheets-Sheet 3 United States Patent O 2,893,335 CU'ITING DEVICE FOR SEWING MACHINE Christiaan Josef Marinus Benink and Karl Kleemann, Kaiserslautern, Pfalz, Germany, assignors to G. M. Pfalf A.G., Kaiserslautern, Pfalz, Germany Application June 25, 1957, Serial No. 667,929

Claims priority, application Germany June 26, 1956 6 Claims. (Cl. 112-125) The present invention relates to a cloth cutting device for sewing machines including a cutter which during sewing operations is rendered operative and retracted by means of an operating lever, and which is moved by means of an activating element mounted in the arm of the machine.

.In cutting devices of the type known heretofore a collapsible guide having guide members is normally provided in the, power transmission between the drive member and the cutter support which, for the purpose of connecting the cutter are stretched out by means of a single operating lever and collapsed for withdrawing the same. In these devices no provision is made for setting the operating stroke of the cutter for the purpose of adapting the cutting stroke to the different types and thicknesses of cloth, nor would such setting or adjustment be readily possible. Consequently, as the 2,893,335 Patented July 7, 195 9 reference to the drawings which illustrate one embodicutter is connected the maximum operating stroke occurs all at once, which results in a considerable connecting jolt.

In another arrangementwhich has become known, means are provided for changing the magnitude of the cutter movements during sewing operations by operating a lever. In this arrangement, however, the construction is necessarily such that either the connecting and the withdrawing of the cutter takes place simultaneously with the change of the cutter stroke which is fixed by stops or that the withdrawing is not possible.

It is an object of the invention to provide a cutting device for sewing machines which permits of stepless setting of the operating stroke between zero and a maximum as well as independent positioning and withdrawing of the inactive cutter during sewing operations by means of a single operating lever.

It is a further object of the invention to provide the possibility of installing'such a cutting device in existing 'sewing machines.

In accordance with the invention a guiding system is provided between the driving element and the cutter support which system is pivotally movable about two axes of rotation, where one of the two axes of rotation is optionally adjustable by a common operating lever for connecting the cutter and setting the magnitude of the cutter movement or for raising and lowering the inoperative or idling cutter. K

These adjustable axes of rotation of the guide system are suitably arranged at one pair of ends of two double armed levers while the other ends under spring pressure engage both sides of a cam secured to a shaft of the switching lever.

In accordance with the invention the adjustable pivot axis for the setting of the magnitude of the stroke of the cutter and a linkage point of a lever which pivots .cutter support is provided with a long slot 47 ment of a cutting device in accordance with the invention and in which:

Fig. 1 is a front view of a sewing machine partly in section exposing the cutting device;

Fig. 2 is a perspective bottom view of the housing with the cover removed;

Fig. 3 is a cut along line III-III in Fig. 1 illustrating the position of the shifting lever for connecting the cutter and zero cutter stroke;

Fig. 4 is a cross section along line IV-IV of Fig. 2 showing the lever in the same position as in Fig. 3;

Fig. 5 is a cross section along line V--V in Fig. 2 with the position of the shifting lever for connected cutter and maximum cutter stroke, and

Fig. 6 is a schematic diagram of the cutting device.

In the drawings the standard 2 of the machine is secured to the base plate 1 and supports the horizontal arm 3 which ends in the head 4. The shaft 5 is journalled in the arm 3, supporting at one end the balance wheel 6 and at its other end the crank 7 which is operatively connected to the needle bar 9 by way of needle bar member 8. A needle 10 is secured to the bottom end at the needle bar 9 which cooperates in a Well known manner with the stitch forming components which are arranged below the base plate and which are not illustrated. The presser-foot bar 11 which is spring biased and carries the presser foot 12 is also disposed in the machine head 4.

A cam 13 forming the drive element for the cutting device is mounted upon arm shaft 5 where it is encompassed by a ring 15 defined endwise of an eccenter bar 14. Eccenter bar 14 projects through an aperture 16 in arm 3 into the interior of the housing 17 which is secured by means of screws to the arm 3 which has a flat lower side. The housing 17 which is open at the bottom is closed by means of a cover 18 secured thereto by screws 20 which engage threaded bores 19. This arrangement of the housing for the switch gear does not in any way interfere with the sewing operation in contrast to the arrangements on the material supporting plate which limit the free passage through the machine by necessary connecting elements to the machine arm.

Two links 22 and 23 are pivotally connected to opposite sides of the eccenter bar 14 by means of bolts 21. The link 22 is rotatably connected by means of a collar screw 24 to a lever 25 which is secured to a shaft 28 journalled in molded conformations 26 and 27 in the housing 17. Link 23 is rotatably secured by means of a collar screw 29 to a lever 30 which is clamped with its sleeve 31 to a pivot shaft 32 by means of screws 33.

A further lever 34 is secured to the shaft 32 which has a split hub 35 at one end with a locking screw 36. The other end of lever 34 is linked to a guide bar 37 which carries at its free end a pivot stud 38 (Fig.5) which is rotatably received in a corresponding bore (not visible in the drawing) of a guide block 39. A slidable sleeve 40 is formed on guide block 39 by means of which the block slides on a guide bar 41 (Figs. land 3 in the head 4 of the machine. 7

A guiding surface 42 (Fig. 2) provided on block 39 which serves for adjusting the cutter support 43 or a cutter 44 (Figs. 1 and 3) with reference to the needle 10 is secured to the block by means of screws 46 received in threaded bores 45. For adjustment purposes the (Fig. 1) through which extend mounting screws 48. 1 1

The cutter 44 is provided with a cutting edge 49 in a known manner (Fig. 3) which coacts with a rigid lower knife 51 embedded in the stitch plate 50, and it is also provided with a guide projection 52. The shaft 32. (Figs. 2 and 3) is journalledat one end in a sleeve 53 on lever 54 which is rotatably mounted in housing 17 by means of a collar screw 55 and at the other end in a sleeve 56 on an arm 57 of a double armed lever 58 (Fig. 4). The latter is mounted on a shaft 59 between two molded conformations or cheeks 26 and 27 and secured by means of a screw 60. The other arm 61 of the double armed lever 58 is curved and rests against a cam 62 which is secured to an operating shaft 63 journalled in the cheeks 26 and 27.

A lever 64 positioned between cheeks 26 and 27 is secured to shaft 28(Figs. 2 and 4) and rests against the side on the cam 62. which is opposite that facing the lever arm 61. A spring 65 maintains lever arm 61 and lever 64 which are proximate one another in continuous engagement with said cam 62. The spring is hooked onto strips 66 and 67 which are secured to levers 61 and 64 by' means of screws.

An operating lever 69 provided with a finger disk 70 is secured by means of a screw 68 (Fig. 2) to the end of operating shaft 63 which projects from housing 17.

As indicated in Fig. 6, lever 25 and the two guide levers 22 and 23 are of the same effective length. The distance of the two shafts 28 and 59 from each other is also of the same length. Furthermore, the two levers 25 and 64 form a double armed lever which is rotatable about shaft 28.

The collar screw 24a at the end of lever 25 constitutes one of the adjustable axes of rotation of the guide system for connecting the cutter 44 and for adjusting the stroke of the knife, while the other adjustable axis of rotation of the guide system for raising and lowering the cutter 44 is formed by shaft 32 which is received in hub or sleeve 56 of lever arm 57 and in sleeve 53 of lever 54.

Figs. 1, 3, 4 and 6 illustrate the position of the operating lever 69 with the cutter 44 lowered and the cutter stroke set at zero. The lever 69 assumes approximately horizontal position for this setting. The two levers 58 and 64 rest against the two sides of cam 62 at minimum spacing from the axis of rotation of shaft 63.

In this position the connection point of lever 23 to lever 30 formed by collar screw 29 is located in the projected axis of rotation 24 of the guide system. The up and down movement of the cam rod 14 during sewing results in rotation of the two links 22 and 23 about this axis of rotation. Inasmuch as the joint 29 is in alignment with the axis of rotation 24 no moment of motion arises in link 23 with the result that the transfer levers 30 and 34 as well as the cutter support 43 are at standstill.

If the operating lever 69 is moved upwardly (Fig. for the purpose ofconnecting in the cutter 44 and for setting the cutter stroke, the double armed lever 25, 64 also effects a corresponding counterclockwise, rotary movement by way of cam 62. The axis of rotation 24 of the linkage or guide system thus is displaced with reference to the linkage joint 29 with the, result that due to the up and down movement of the cam rod 14, link 22 effects a true rotary movement about axis of rotation 24, whereas link 23 in addition to this rotary movement is subjected to a movement in longitudinal direction. As a result levers 30 and 34 are caused to efiect a pivotal movement about shaft 32, i.e. about the other axis of rotation of the linkage system. The greater the movement of lever 69 upwardly, the greater will be the distance of the axis of rotation 24 from linkage joint 29 and the greater will be the stroke of the cutter.

It is possible in this manner to continuously adjust the stroke of the cutter. With the described displacement of the operating lever the position of the double armed lever 58 is maintained because its arm 61 rests against the concentric part of cam, 62.

In order to raise the cutter 44 the operating lever 69 as looked at in Figs. 3 to 5 is moved clockwise. The cam 62 rotates the double armed lever 58 in the same direction. As a result the shaft 32 with levers 30 and 34 is moved clockwise about shaft 59 of double armed lever 58 and about collar screw 55 of the lever 54. Thus the cutter support 43 is raised to its inoperative position. Since axisof' rotation 24 and linkage joint 29 coincide withthe pivot axes 55 and 59 of shaft 32 the cutter 44 dojesv not effect any oscillatory movements in the raised position. The double armed lever 25, 64 remains in the position shown in Figs. 4, and 6 during the described displacement of operating lever 69 because its lever arm 64 rests against the concentric portion of the cam 62.

When the cutter stroke is changed the cutter movement can take place either from the zero position of the cutter 44 or upwardly or downwardly with reference to the zero position. With the cutter device in accordance with the invention this depends. merely on the position of the axis of rotation of shaft 28 in relation to the axis of rotation of cam 13.

For example, if the distance of the axis of rotation of shaft 28 from that of the cam is equal to the effective length of the cam rod 14 the cutter 44 effects movements about its zero position. Decreasing or increasing this distance by the amount of eccentricity of the cam 13 with reference to the effective length of the cam rod 14 causes the movement of the cutter with reference to the zero position of the cutter 44 to continue only upwardly or downwardly as the stroke is changed. The same elfect is,-of course, obtained if the effective length of the cam bar 14 is changed instead of the distance.

In practice, the cutter stroke displacement is only effected in the upward direction and the zero position of the cutter is located in such a manner that the cutting edge 49 assumes approximately the position shown in Fig. 3.

Having now described our invention with reference to the embodiment illustrated in the drawings we do not wish to be limited thereto but what we claim as our invention is set forth in the appended claims.

1. A cutting mechanism for a sewing machine having a drive shaft and an overhanging arm comprising a housing adapted to be supported on the arm of the machine, guiding linkage including a first and a second double armed lever pivotally supported in said housing each having one arm extending proximate an arm of the other, a cutter mounted for reciprocating movement at at one end of and below said housing and operatively connected to said guiding linkage, cam operated driving means for said mechanism adapted to he linked to the drive shaft of the machine, an operating lever pivotally mounted in and extending with one end externally of said housing and having at its other end a rotatable member operatively connected with said proximate arms of said double armed levers, said linkage including a lever member pivotally supported at one end in said housing in axial alignment with the pivot axis of said firstdouble armed lever, a shaft extending between said lever member and the other arm of said first double armed lever and movable therewith, said shaft presenting a first radially extending lever arm operatively connected to said cutter and a second radially extending lever arm, a pair of links of equal length pivotally connected at corresponding ends of saiddriving means, the other: end of one said being of the same length as and pivotally connected to the other arm of said second double armed lever and the other end of the other said link being pivotally connected to the end of said second radiallyextending lever arm.

2 A cutting mechanism for a sewing machine having a, drive shaft and: an overhanging arm comprising a housing adapted. to, be, supported on the arm of the machi e. guiding linkage including a first and a second doublev armed. leverpivotally supported in said housing each having one arm extending proximate an arm of the other, a cutter mounted for reciprocating movement at at one end of and belowsaid housing and operatively connected to said guiding linkage, cam operated driving means for said mechanism adapted to be linked to the drive shaft ofthe machine, an operating lever pivotally mounted in and extending with one end externally of said housing and having at its other end a rotatable member operatively connected with said proximate arms of said double armed levers, said linkage including a lever member pivotally supported at one end in said housing in axial alignment with the pivot axis of said first double armed lever, a shaft extending between said lever member and the other arm of said first double armed lever and movable therewith, said shaft presenting a first radially; extending lever arm operatively connected to said cutter and a second radially extending lever arm, a pair oflinks of equal length pivotally'connected at corresponding ends of said driving means, the other endof one said link being of the same length as and pivotally connected to the other arm of said second double armed lever and the other end of the other said link being pivotally connected to the end of said second radially extending lever arm, said rotatable member being a cam and said proximate arms of said double armed levers being spring biased to rest against said cam.

3. A cutting mechanism for a sewing machine having a drive shaft and an overhanging arm comprising a housing adapted to be supported on the arm of the machine, guiding linkage including a first and a second double armed lever pivotally supported in said housing each having one arm extending proximate an arm of the other, a cutter mounted for reciprocating movement at at one end of and below said housing and operatively connected to said guiding linkage, cam operated driving means for said mechanism adapted to be linked to the drive shaft of the machine, an operating lever pivotally mounted in and extending with one end externally of said housing and having at its other end a rotatable member operatively connected with said proximate arms of said double armed levers, said linkage including a lever member pivotally supported at one end in said housing in axial alignment with the pivot axis of said first double armed lever, a shaft extending between said lever member and the other arm of said first double armed lever and movable therewith, said shaft presenting a first radially extending lever arm operatively connected to said cutter and a second radially extending lever arm, a pair of links of equal length pivotally connected at corresponding ends of said driving means, the other end of one said link being of the same length as and pivotally connected to the other arm of said second double armed lever and the other end of the other said link being pivotally connected to the end of said second radially extending lever arm, the other ends of said first and second double armed levers defining movable pivot axes and being alternately movable by said operating lever by way of said cam, said pivot axis endwise of said first double armed lever being operative to raise said cutter to inoperative position and said pivot axis of said second double armed lever being operative for connecting said cutter and for setting the magnitude of the cutter movement.

4. A cutting mechanism for a sewing machine having a drive shaft and an overhanging arm comprising a housing adapted to be supported on the arm of the machine, guiding linkage including a first and a second double armed lever pivotally supported in said housing each having one arm extending proximate an arm of the other, a cutter mounted for reciprocating movement at at one end of and below said housing and operatively connected to said guiding linkage, cam operated driving means for said mechanism adapted to be linked to the drive shaft of the machine, an operating lever pivotally mounted in and extending with one end externally of said housing and having at its other end a rotatable member operatively connected with said proximate arms of said double armed levers, said linkage including a lever member pivotally supported at one end in said housing in axial alignment with the pivot axis of said first double armed lever, a shaft extending between said lever member and the other arm of said first double armed lever and movable therewith, said shaft presenting a first radially extending lever arm operatively connected to said cutter and a second radially extending lever arm, a pair of links of equal length pivotally connected at corresponding ends lOf said driving means, the other end of one said link being of the same length as and pivotally connected to the other arm of said second double armed lever and the other end of the other said link being pivotally connected to the end of said second radially extending lever arm, said rotatable member being a cam and said proximate arms of said double armed levers being spring biased to rest against said cam, the other ends of said first and second double armed levers defining movable pivot axes and being alternately movable 'by said operating lever by way of said cam, said pivot axis endwise of said first double armed lever being operative to raise said cutter to inoperative position and said pivot axis of said second double armed lever being operative for connecting said cutter and for setting the magnitude of the cutter movement.

5. A cutting mechanism for a sewing machine having a drive shaft and an overhanging arm comprising a housing adapted to be supported on the arm of the machine, guiding linkage including a first and a second double armed lever pivotally supported in said housing each having one arm extending proximate an arm of the other, a cutter mounted for reciprocating movement at one end of and below said housing and operatively connected to said guiding linkage, cam operated driving means for said mechanism adapted to be linked to the drive shaft of the machine, an operating lever pivotally mounted in and extending with one end externally of said housing and having at its other end a rotatable member operatively connected with said proximate arms of said double armed levers, said linkage including a lever member pivotally supported at one end in said housing in axial alignment with the pivot axis of said first double armed lever, a shaft extending between said lever member and the other arm of said first double armed lever and movable therewith, said shaft presenting a first radially extending lever arm operatively connected to said cutter and a second radially extending lever arm, a pair of links of equal length pivotally connected at corresponding ends to said driving means, the other end of one said link being of the same length as and pivotally connected to the other arm of said second double armed lever and the other end of the other said link being pivotally connected to the end of said second radially extending lever arm, the other ends of said first and second double armed levers defining movable pivot axes and being alternately movable by said operating lever by Way of said cam, said pivot axis endwise of said first double armed lever being operative to raise said cutter to inoperative position and said pivot axis of said second double armed lever being operative for connecting said cutter and for setting the magnitude of the cutter movement, the pivotal connection of said pair of links and said driving means being in axial alignment with the pivot axis of said second double armed lever for the neutral position and for the inoperative position of said cutter.

6. A cutting mechanism for a sewing machine having a drive shaft and an overhanging arm comprising a housing adapted to be supported on the arm of the machine, guiding linkage including a first and a second double armed lever pivotally supported in said housing each having one arm extending proximate an arm of the other, a cutter mounted for reciprocating movement at one end of and below said housing and operatively con- 7 nected to said guiding linkage, cam operated driving means for said mechanism adapted to be linked to the drive shaft of the machine, an operating lever pivotally mounted in and extending with one end externally of said housing and having at its other end a rotatable member operatively connected with said proximate arms of said double armed levers, said linkage including a lever member pivotally supported at one end in said housing in axial alignment with the pivot axis of said first double armed lever, a shaft extending between said lever member and the other arm of said first double armed lever and movable therewith, said shaft presenting a first radially extending lever arm operatively connected to said cutter and a second radially extending lever arm, a pair of links of equal length pivotally connected at corresponding ends to said driving means, the other end of one said link being of the same length as and pivotally connected tothe other arm of said second double armed lever and the other end of the other said link being pivotally connected to the end of said second radially extending lever arm, said rotatable member being a cam and said proximate arms of said doubler armed levers being spring biased.

to rest against said cam,.the' other vends of said first second double armed levers defining movable pivot. axes and being; alternately. movable by said operating lever byway of said cam, said pivot axis endwis'e' of said first; double armed lever being operative to raise said cutter to inoperative position and said pivot axis of said second double armed lever being operative for connecting said cutter and for setting the magnitude of the cutter movement, thepivotal connection of said pair of links and said driving means being in axial alignment with the pivot axis of said second double armed-leverfor the neutral position and for the inoperative position of said cutter.

References Cited in the file of this patent UNITED STATES PATENTS Stevenson July 11, 1939 

